🧭 How to Set Up a Crank Sensor RPM Signal in a TurboLamik TCU

Setting up an RPM signal in a TurboLamik TCU might sound simple, but it’s one of the most misunderstood parts of the install.
The TCU depends heavily on a clean, fast, and correctly scaled crank signal to operate the 8HP transmission reliably — not just to read RPM, but to correctly calculate converter slip and control clutch pressures.

This guide explains how a crank signal works, what the TurboLamik expects, how to wire and calibrate it correctly, and how to verify it’s behaving properly.

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⚙️ 1. Understanding the Crank Sensor Signal

Engines use one of two main sensor types to read crankshaft position:

• VR (Variable Reluctance) sensors generate their own voltage — an AC waveform that increases in amplitude with RPM. These are simple 2-wire sensors.

• Hall-effect sensors are powered (3-wire) and output a digital square wave every time a tooth passes. Depending on design, they can output 0–5 V or 0–battery voltage (≈ 12 V).

👉 The TurboLamik expects a 0–5 V square-wave signal on Pin 65.
This doesn’t mean you can’t use a crank sensor directly — it just means the sensor must be electrically compatible with that input.

• If your sensor outputs a clean 0–5 V square wave, you can wire it directly.

• If it’s a 12 V Hall or VR sensor, you’ll need a signal conditioner or use an ECU tach/engine-speed output configured for 5 V logic.

Always share a common ground between the signal source and the TCU.

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⚡ 2. The Importance of Tooth Count and Update Rate

The 8HP transmission relies on the engine RPM signal for torque converter slip and clutch control.
The TCU constantly compares engine speed (from Pin 65) against input shaft speed (measured internally).

If the engine speed signal updates too slowly — for example, if the trigger wheel only has a few teeth — the TCU can misinterpret acceleration as deceleration because the input shaft speed updates much faster.
When that happens, the TCU may reduce clutch pressure or unlock the converter, causing flares or slip.

To avoid this:

• Use a high-resolution crank wheel (36-1 or 60-2).

• Make sure the signal has fast, clean transitions.

• Avoid using low-resolution or heavily filtered outputs such as cam sensors or tach feeds.

The TCU needs the RPM signal to refresh at least as quickly as the transmission’s internal speed sensors for correct torque and pressure control, be wary of anything under 20 teeth, it does not take long to damage a transmission.

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🔌 3. Wiring the RPM Input

A floating or noisy ground will cause erratic RPM readings, especially at low speed.

We have had success simply piggy backing on to the sensor output from the OEM ecu. In case you simply connect the sensor output to pin 65.

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⚙️ 4. Calibrating the Signal in TurboLamik

Once you have a signal on Pin 65, it must be calibrated in the software so the TCU interprets it correctly.
There are three main parameters:

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1️⃣ Engine Speed Input Filtering

This defines how often the TCU samples the signal per crank revolution.

Rule of thumb:
Set this to the same number of teeth on your crank wheel.
Example:

• 60-2 → set to 58

• 36-1 → set to 35

A value that’s too low causes missed teeth. Too high can oversample noise or produce false readings.

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2️⃣ Engine Speed Input (Tooth Count)

Enter the number of actual teeth the sensor sees per crank revolution.
For missing-tooth wheels, count only the real teeth.

Incorrect values here will cause the RPM to display wrong and the converter slip to calculate incorrectly.

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3️⃣ Engine Speed Input Voltage Threshold

This sets the trigger point — the voltage at which the TCU registers each tooth.

Because the TurboLamik software doesn’t display a live waveform, you’ll need an oscilloscope to view the signal directly.

How to set it:

1. Connect the oscilloscope probe to the crank signal close to the TCU and the ground clip to signal ground.

2. Crank or start the engine.

3. Observe the waveform and note its peak voltage.

   • Many OEM Hall sensors peak around 2.5 V.

4. Set the threshold slightly below that — e.g., 2.3 V for a 2.5 V signal.

   • For 5 V square waves, use around 4.7 V.

This ensures each rising edge of the pulse crosses the threshold cleanly.

If the threshold is:

• Too high → missed teeth at low RPM

• Too low → noise triggers false counts

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Example Settings for a 60-2 Wheel

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📈 Waveform Example

Below is a typical Hall-sensor waveform.
Each rising edge that crosses the threshold (2.3 V) represents a detected tooth.
The high section corresponds to the tooth, and the low section is the gap between teeth. This can vary depending on trigger wheel.

 

 

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⚠️ 5. Don’t Use a Slow or Filtered Tacho Output

Although it’s possible to feed an RPM signal from an ECU’s tacho output, this is not recommended.
Tacho outputs are heavily filtered and update too slowly for TCU use.
We are aware of at least one case where a slow tacho signal caused clutch control faults and transmission damage.

The TurboLamik requires a fast, high-frequency signal to keep up with the input shaft sensor inside the 8HP.
If the RPM lags, the TCU can misread acceleration and incorrectly reduce clutch pressure.

✅ Always use:

• A direct crank sensor signal (if 5 V compatible), or

• An ECU digital output configured as a fast engine-speed signal

Avoid any output designed for a gauge, dash, or CAN translator unless verified for update speed.

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🧠 6. Sanity Check in TurboLamik

Once configured, perform a quick validation with live data in TunerPro:

1. With the engine idling, view Engine Speed and Input Shaft Speed.

   • The engine speed should be slightly higher due to converter loses.

2. Slowly raise the throttle — hold at 1000 → 1500 → 2000 RPM.

   • The difference between the two should reduce smoothly as the converter couples.

3. If engine RPM appears to lag or jump, check your signal threshold, ground, and tooth count.

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🧩 Final Summary

• TurboLamik expects a clean 0–5 V square-wave signal on Pin 65

• Use a high-resolution crank wheel (36-1 / 60-2)

• Calibrate:

  • Filtering: equal to tooth count

  • Input (Tooth Count): number of real teeth

  • Voltage Threshold: slightly below waveform peak

• Verify signal with an oscilloscope — don’t guess

• Never use a slow tacho output; it can cause clutch or converter damage

• Check engine vs input shaft speed to confirm healthy signal behavior